Lemma 2.4 
[1]} For any \(\delta >0\) , there exists a constant \(C_{\delta }\)  such that
\(|\tau (g)|^2\le \delta \Vert \nabla _{R}g\Vert ^2_{\mathcal {L}^{2}}+C_{\delta }\Vert g\Vert ^2_{\mathcal {L}^{2}}.\) 
